FIG. 1 is an assembly 9 of an auto-injector 91 and a cell phone 92 disclosed in U.S. Pat. No. 8,639,288 B1. However, the disclosed assembly 9 is difficult to operate. Besides, in known auto-injectors (such as that disclosed in US 2012-0220954 A1), a needle of the auto-injector is in fluid communication with a medicament container. Alternatively, the needle is arranged to penetrate a septum of the medicament container prior to penetrating a user's tissue. Such prior art auto-injectors will result in medicament leakage outside the user's body so that the user will not obtain a sufficient dose of medicament. In other words, the disclosed auto-injector is difficult to control to get an accurate dose.